1. Field of the Invention
The present invention relates to a heat-dissipating device, and in particular to a centrifugal fan and its housing for increasing airflow pressure.
2. Description of the Related Art
In FIG. 1, a conventional blower 1 includes a frame 10, a motor 20 and an impeller 30. The frame 10 includes an air inlet 11 and an air outlet (not shown). The motor 20 is disposed on a base 101 of the frame 10 to drive the impeller 30. The impeller 30 includes a hub 31, a base plate 32 and a plurality of blades 33 disposed on the base plate 32. The blades 33 are circumferentially disposed around the hub 31.
The blades 33, however, are located in the passage of airflow and gaps therebetween are large such that the direction of airflow cannot be properly controlled during operation. Thus, it is possible to cause the output airflow to flow back to the blower, thereby decreasing heat-dissipating efficiency thereof.
To increase heat-dissipating efficiency for a high performance electronic device, an inner airflow passage is often enlarged to increase the volume of airflow. The size of the inner passage of airflow, however, is limited by the space of the applied system, creating problems such as unbalanced airflow, noise and reduced output.
It is beneficial to increase the number and size of blades to enhance airflow volume, but limits are still imposed by the limited space of the blower, with heat-dissipating efficiency decreased accordingly.